The A1 in London is an A road in North London. It runs from the London Wall to Bignell's Corner, where it crosses the M25 and becomes the A1(M) motorway, continuing to Edinburgh. (For the road outside London, see the main A1 road article.) The London section passes through 4 London Boroughs: the City of London, Islington, Haringey and Barnet. Whilst the route of the A1 outside London closely follows the historic route of the Great North Road, the London section for the most part does not.
The current route of the London section of the A1 road was (for the most part) designated as such in 1927. It comprises a number of historic streets in central London and the former suburbs of Islington, Holloway and Highgate and long stretches of purpose-built new roads in the outer London borough of Barnet, built to divert traffic away from the congested suburbs of Finchley and High Barnet.